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天线自动跟踪技术是卫星移动通信系统的关键技术,其核心问题是天线对卫星的快速捕获和自动跟踪.文中采用了新的步进跟踪算法,进一步提高了系统的跟踪速度和精度. 相似文献
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Xingyu Wang Shanghong Zhao Yongjun Li Zhuodan Zhu Yongxing Zheng Chen Yu 《International Journal of Satellite Communications and Networking》2020,38(3):272-283
Data relay satellite (DRS) systems play an important role in space information networks. Characterized by highly dynamic topology and discontinuous communication links, it is suggested that the IEEE 802.11 protocol employed in such a network could be more flexible. However, such a terrestrial network protocol could not be applied to DRS systems directly, nor supports a fast response due to the long propagation delay and severe packet collision. To address this challenge, we proposed an enhanced media access control (MAC) protocol based on the IEEE 802.11 protocol providing multiaccess for low earth orbit (LEO) distributed constellations. In this paper, we investigated the access delay performance of the proposed protocol in our model. Then, we derived a contention window adaption by using an iteration algorithm that can dynamically adjust the values of the contention window depending on the number of user satellites in the communication coverage. Simulation results show that the average access delay does not exceed 20 seconds, which is significantly lower than the standard protocol. Moreover, the traffic threshold is increased to 0.6, and the maximum throughput has doubled compared with the standard protocol. It is proved that the enhanced MAC protocol shows a better performance in DRS systems. 相似文献
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为满足中继卫星系统对天线指向精度的要求,首先描述了天线指向控制概念,对用户星与中继卫星星间链路的建立过程进行了分析,并且设计了星上自主控制方案,在Simulink环境下对所设计的天线指向控制系统进行了数学仿真,最后通过对仿真结果的分析验证了用户星天线控制系统的跟踪性能。 相似文献
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天线跟踪功能是车载动中通系统( SOTM)提供无线通信能力的前提,相控阵天线能提供较好的跟踪性能,但是存在波束扫描范围有限的问题。为实现相控阵天线全方位跟踪能力,提出了一种相控阵+伺服辅助的方法。给出了算法数据处理流程,并完成了原理样机设计。根据原理样机工作原理给出了跟踪角误差计算公式,测试结果与计算结果相符。测试结果表明:在(57.88~115.76)。/s角速度下,通信链路信噪比损失小于0.5 dB。 相似文献
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An analysis is presented of a balanced quadricorrelator driven by a digital-modulated signal with thermal noise. The aim is to assess its performance as a frequency difference detector. The circuit output is decomposed into a signal term and a disturbance referred to as noise. Exprssions are given for the signal and for the power spectral density of the noise as a function of the various system parameters. Design criteria are provided to minimize the output noise for zero frequency offset. In particular, it is found that at high signal-to-noise ratios the noise level can be made vanishingly small by the proper choice of the quadricorrelator filters. A similar result has been recently discovered for another frequency difference detector, the dual-filter detector. It is shown that a balanced quadricorrelator and a dual-filter detector can be made totally equivalent 相似文献
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Manuel Roth Hartmut Brandt Hermann Bischl 《International Journal of Satellite Communications and Networking》2021,39(1):92-107
A major problem for low Earth orbit (LEO) constellations with intersatellite links is the efficient routing of the data packets through such a highly dynamic network. In order to achieve a worldwide coverage even in remote areas and Internet access with a limited amount of gateway stations, intersatellite links are a promising approach. Since LEO constellations represent a distinct, highly dynamic routing environment, specific strategies are needed. To this end, a suitable geographical routing scheme is proposed and investigated in two Walker Star constellations. The proposed scheme targets reliable transmissions with low latency and high data rates. The approach is based on a geographical address identifier in Layer 2 of the communication stack. The globe is thus divided into geographical areas that determine this identifier in the MAC address of the terminals. As mobile terminals are considered, the MAC addressing scheme is flexible, whereas the IP addresses of the terminals remain static. This decoupling allows for flexibility in the choice of the address resolution scheme. Moreover, the geographical identifier in the MAC address enables fast routing table lookups and switching. The proposed routing scheme also takes possible overloads of the satellites due to traffic into account and applies a rerouting procedure. When a packet arrives in the geographical area of the destination terminal, a local rerouting scheme is applied if needed. The proposed approaches take handover events that possibly occur during a transmission into account. Furthermore, the scan angles of the satellites have been adapted to the constellations to provide full coverage and high elevation angles. So a robust and adaptable routing scheme is provided for a dynamic environment where satellites and terminals are constantly moving. The proposed definitions and procedures have been implemented in a system level simulator, which allows for comparisons with adjustable parameters in various scenarios. In this work, an Iridium‐like constellation and a megaconstellation are investigated and compared regarding the address resolution procedures, the average end‐to‐end transmission delay, and the dropping and rerouting rates. Additionally, the signaling overhead is compared with other approaches. The simulator and results of the simulations provide grounds for further research w.r.t. the routing in satellite constellations using intersatellite links. 相似文献
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One of the fundamental constraints in radio frequency identification (RFID) large scale deployment, such as in warehouse RFID deployment, is the positioning of RFID reader antennas to efficiently locate all the tagged objects distributed in a dense RFID reader environment. For tracking the tagged objects in a dense RFID deployment, the required number of reader antennas must be optimised in order to reduce the overall cost. This study proposes highly accurate square and hexagonal grid-based positioning and tracking techniques mainly for use indoors and includes performance comparison of both of these grids. The study involves the design of the square and hexagonal grid reader antenna networks and position calculation using a diffusion algorithm. Both of these grids of RFID antenna positioning present a solution for the problem of the placement pattern of RFID reader antennas in a dense reader environment, hence an optimal number of required reader antennas and guaranteed coverage can be achieved. This study also presents a path loss model that can be applied to predict the radio signal strength information at a certain distance. The proposed diffusion algorithm estimates RFID tag position by using distance information between the reader and the tag. The obtained results show that a square grid can yield higher positioning accuracy compared to the hexagonal grid. The obtained results further show that the proposed tracking techniques can achieve an average positioning error below 1 m, which is 85% better in some cases than the results obtained by other known methods. 相似文献
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基于航天事业的发展和测控的需求,地面测控网布设的密度越来越大,范围越来越广。为了更好了解和掌握卫星以及航天飞行器在轨运行状况,就需要通过测控天线的精确跟踪来完成。文中对当前测控与雷达天线的几种跟踪方式进行了介绍、分析,并结合未来环境的复杂和多变性,对测控与雷达领域跟踪技术的发展趋势进行了展望。 相似文献
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针对高码率低轨卫星测控的需求,给出了一种新型三轴12 m X/Ka频段天线的设计思路,通过优化反射面结构型式、材料选择、力学分析、减轻重量,提高天线反射体的精度;进行天线座架驱动链路设计和刚度设计,提高天线系统的谐振频率;通过优化伺服控制与伺服选型设计,提高伺服跟踪控制性能。基于Nastran/Patran有限元软件,对多种工况下的天线承载结构进行了刚度分析、强度分析、面型精度分析与结构固有频率等分析,结果表明典型仰角下的天线主面精度、承载能力及谐振频率均满足要求。依据有限元分析结果,采用高精度碳纤维天线反射体、高刚度A-E-T三轴天线座架、大动态伺服控制的设计方案,合理设计了12 m反射面天线的整体结构形式以及连接形式,并进行了天线实物的加工。所设计加工的12 m反射面天线满足高精度、高刚度、过顶跟踪的性能指标要求,对中大口径天线的设计具有一定的参考意义。 相似文献
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空基测控中继是为解决地面测控设备作用距离受视距限制的问题而提出的,而相控阵天线是空基测控中继设备的技术难点。根据实际需求,提出了相控阵天线的设计方案,对阵列形式、天线的流形、阵元间距、阵列规模以及阵元形式等进行了详细设计,并对天线的接收发射性能进行了仿真,对跟踪控制技术途径进行了阐述。所设计的相控阵天线增益可以满足约130 km、2 Mbit/s遥测数据中继,解决远距离低空飞行目标的靶场测控问题。 相似文献
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本文针对线天线及天线阵的频域分析方法的缺点,首次将时域传输线矩阵法应用到这一领域,应用时域TLM法时,只需经过一次运逄就可以得到天线及天线阵各个区域的场特性,本文计算方法及数值结果表明,运用时域TLM法可以对各种大型天线阵进行有效的分析,便于工程应用。 相似文献
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一种新型平面阿基米德螺旋天线的分析与设计 总被引:1,自引:0,他引:1
对一种新型的平面阿基米德螺旋天线--锯齿状平面阿基米德螺旋天线进行了研究。首先给出了该天线的几何结构,介绍了其主要特点和应用领域,设计并制作了一个2.9~6.2GHz的锯齿状平面阿基米德螺旋天线。测试表明,与普通平面阿基米德螺旋天线相比,该天线能够缩小尺寸,展宽频带,很好地改善天线的低频特性。 相似文献
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Zoltn Katona Michael Grßlin Anton Donner Norman Kranich Hartmut Brandt Hermann Bischl Martin Brück 《International Journal of Satellite Communications and Networking》2020,38(3):301-313
From a geostationary Earth orbit (GEO) satellite's perspective, a low Earth orbit (LEO) satellite is visible on more than half of its orbit. Albeit the free‐space loss of an inter‐satellite link is much higher than the one of a direct ground link, considerable data rates and download volumes can be achieved. In this paper, we describe the system architecture of an integrated approach for a data relay satellite system and the development of LEO satellite and ground station modems. The approach allows serving several small and inexpensive LEO satellites at the same time both with low rate telemetry/telecommand links and with high rate download of sensor data. 相似文献